Adam Dickler, MD
Intraoperative radiation therapy (IORT) is an experimental way to deliver radiation as part of breast conservation therapy. If IORT is found to be equivalent to whole breast irradiation, this could mean more convenient care for patients, reduced waiting times, and considerable savings for health-care systems. However, a lack of long-term clinical data and reimbursement issues are holding back the widespread adoption of this modality.
Radiation oncologist Adam Dickler, M.D., of the Little Company of Mary Hospital, discusses his center’s experience with IORT, how it compares to outpatient APBI and what it means for the future of breast cancer treatment.
How long have you been offering IORT as a treatment option for breast cancer?
We started treating patients on a protocol using Xoft IORT in September 2008. It began as a single institution trial at Little Company of Mary Hospital, but since then other institutions have expressed interest in participating. As a result, we have expanded it to a national, multi-center trial. The early results in the patients treated in our study have been very favorable. To date, there have been no local recurrences and 100 percent of the patients have achieved good or excellent cosmesis. Toxicity has been minor and infrequent.
In which patients do you find IORT to be most useful/appropriate?
Any patient who is eligible for outpatient APBI based upon pathologic criteria is also eligible for enrollment in our IORT trial. I find IORT particularly useful for patients who may not otherwise undergo radiation, anyone who may get lumpectomy alone without the follow-up radiation. For example, in certain elderly patients even five days of outpatient treatments would be a burden. Radiation is an important component of breast conserving therapy, and has been shown to improve overall survival.
Careful patient selection is essential for the successful delivery of IORT. To qualify for the trial, patients must be 50 years or older, have unifocal infiltrating ductal carcinoma or DCIS, tumors 3-cm or smaller, a negative sentinel lymph node biopsy by frozen section at the time of surgery, and lumpectomy cavities with at least 1 cm of skin distance based upon intraoperative ultrasound.
How are patients managed that are found to have positive margins after completing IORT?
The lack of real-time pathology means you can’t be sure about the margin status until a few days after the surgery when a final pathologic review can be performed. If a patient were found to have positive margins following IORT, we would offer them whole breast radiation and consider the IORT to be the tumor bed boost.
To date, we have not had patients with positive margins on final pathologic review in our study. Careful patient selection is extremely important. We utilize preoperative MRI to help identify patients with unifocal disease.
What are your thoughts on the current body of research on the use of IORT for treating breast cancer? Do you feel there is sufficient clinical evidence to say it is equivalent to whole breast radiation?
The early data on IORT looks very good. Especially encouraging is the TARGIT trial which shows favorable cancer control and toxicity profile. However, I still consider IORT to be experimental, and I would only perform it under an IRB-approved protocol. At this point, I think the consensus among the radiation oncology community is that it’s still a research modality and more clinical data needs to be acquired before it can be considered a standard of care.
How does IORT compare to breast brachytherapy?
I see a few benefits of IORT. First is the convenience factor – the patient potentially completes all of their radiation before they wake up from surgery. Second, you deliver radiation before the cancer cells have a chance to multiply. Third, it’s done under direct visualization at the time of surgery. But the biggest disadvantage of IORT is the lack of real-time pathology and not knowing until several days later if the patient has involved margins. There are currently technologies that allow for real-time margin assessment, but until these are widely available this will continue to be a limitation for the adoption of IORT.
In our study, the side effect profile of IORT has been similar to brachytherapy. At short follow-up, we are seeing slightly better cosmesis but this is likely, at least in part, due to limiting the study to patients with at least a 1 cm balloon-to-skin distance. Overall, I don’t see brachytherapy and IORT as competing modalities. Rather, they are complementary modalities for the treatment of early-stage breast cancer. No single treatment method is ideal for all patients.
How do you measure the depth of penetration with IORT? Does the size of the target volume differ for IORT and breast brachytherapy?
We developed treatment plans using CT scans of the balloon catheter in a water phantom that determine the radiation depth doses based upon source parameters from the manufacturer. We developed treatment plans for four different sizes of balloons (40 cc, 50 cc, 60 cc and 70 cc), which are brought into the operating room on a jump drive. The appropriate plan is loaded onto the machine, depending on the size of the lumpectomy cavity. For balloon-based APBI, the dose is prescribed to a 1 cm depth. In our study, we prescribed it to the balloon surface and also recorded the dose at the 1 cm depth
What challenges do you see for widespread adoption of IORT?
Right now, major challenges include the need for further work on reimbursement of the procedure and the ability to determine margin-status in the OR. Probably the single most important item, though, is the need to see long-term clinical data. Until this is available, IORT for early-stage breast cancer should only be performed on an IRB approved trial.
Dr. Dickler practices at the Little Company of Mary Hospital & Health Care Centers in Evergreen Park, IL. His clinical interests are partial breast irradiation, prostate cancer, and general radiation oncology.